Combination lock extraction apparatus

ABSTRACT

The following specification describes a plurality of combination lock cylinders, each of the axially movable tumbler pin type and each having a drive plate initially rotatable in a selected one of two directions by the tumbler operating pins of a respective operating key to control a bolt. A lock cylinder extraction key having tumbler pins universal to each lock cylinder rotates the drive plate in the direction opposite the selected direction to align a slot in the drive plate with a boss in the housing for enabling removal of a respective lock cylinder from its housing. 
     Each lock cylinder has one pair of bayonet slots extending in the selected direction and engaged only by bayonet pins on the respective operating key for enabling rotation of the drive plate only in the selected direction and another pair of axially offset bayonet slots extending in the opposite direction and engaged only by bayonet pins on the lock cylinder extraction key to enable rotation of the drive plate only in the opposite direction.

FIELD OF THE INVENTION

This invention relates in general to lock extraction apparatus and moreparticularly to improved and more economical lock extraction apparatusfor use with combination locks of the axially movable tumbler pin typesuch as, for example, employed in the control of switchbear.

SUMMARY OF THE PRIOR ART

Combination locks of the axially movable type are widely used for accessor control purposes. Such locks or lock cylinders employ tumbler pinswhich are moved axially by an operating key carrying a combination ofpins projecting a distance correspondence to the axial travel of thetumbler pins required to enable rotation. When the tumbler pins aremoved axially to a proper position, the operating key may be rotated ina selected direction to rotate the lock tumbler barrel and move the lockbolt.

In order to extract such combination lock from the front of its housing,one procedure utilizes an extraction key carrying a combination ofprojecting pins corresponding to the respective operating key. Theextraction key is engaged with the lock cylinder and the operator mayrotate the tumbler barrel in either direction and when the desiredalignment is secured between a movable lock part and a portion of thelock housing, removal of the lock cylinder is permitted. The extractionkey however is not universal or mastered to a large member of lockcylinders, nor is the position to which the extraction key operates thetumbler barrel fixed so that some manipulation may be required. Afurther problem arises in some applications as the tumbler barrel can beoptionally rotated in either direction by an extraction key. This typeof arrangement may be hazardous in some situations.

As an example, to enable or disable selected apparatus such asswitchgear, each piece of apparatus is provided with one or more locksor lock cylinders each controlled by a respective operating key to inturn permit movement of a common bolt for controlling the associatedapparatus. For safety reasons the operating keys are provided authorizedpersonnel only and initial rotation of the respective tumbler barrel ispermitted in only a selected direction. It may under these circumstancesbe hazardous to use an extraction key, which can rotate the tumblerbarrel in either direction.

Under many circumstances it is desired to ensure that one piece ofapparatus be in a desired condition before the condition of anotherpiece of apparatus be altered. To ensure the proper condition of eachpiece of apparatus one or more operating keys are releasable from theirrespective lock only if other locks at that apparatus are properlyconditioned.

The released operating key or keys can then be removed for operating arespective lock at the other apparatus. This ensures that each piece ofapparatus is properly conditioned before the condition of another pieceof apparatus can be changed. However if the sequence in which control isexercised over the apparatus or if other apparatus is to be controlledby an operating key common to several pieces of apparatus in the same oranother sequence, changes in the lock cylinders may be required.

Since an extraction tool of the type described above may rotate thetumbler barrel in either direction its use presents safety problems forsome applications. The practice therefore with combination locks of theaxially movable pin type when used for purposes such as described is topress fit the lock cylinders in their housings and permit initialrotation by an operating key only in the selected direction. When a lockchange is required, it is therefore necessary to replace the entire lockand housing assembly. This can be quite expensive since a large numberof locks may be provided in a single housing.

SUMMARY OF THE INVENTION

The present invention utilizes a combination lock of the axially movablepin type having a tumbler barrel, which is rotatable by an extractionkey only in a direction opposite that in which the lock is rotated byany operating key to eliminate any safety problems.

The invention further utilizes an extraction key universal to a largenumber of combination locks of the axially movable pin type. The oneextraction key can therefore extract a selected large number ofcombination locks. The direction of rotation and angular distance ofrotation are also automatically controlled so that each lock is easilyand conveniently removed from the front of the housing. This arrangementprovides a simple inexpensive and improved extraction procedure forgeneral use with combination locks of the axially movable pin type.

Controlling the direction of rotation is accomplished by providing eachlock cylinder with two pair of axially offset bayonet grooves or slots.One pair of slots extend arcuately in one direction and are engaged bybayonet pins on the operating key to enable initial rotation of thedrive plate in the selected direction to control the bolt and the otherpair of slots extend arcuately in the opposite direction. The other pairof slots are engaged by bayonet pins on the extraction key to enableinitial rotation of the drive plate only in the opposite direction fordisengaging the lock cylinder from the housing. The bayonet pins of theextraction and operating keys are offset from their operating pins by adistance corresponding to the offset in the bayonet slots so that eachmoves the lock tumbler pins the proper distance when the bayonet pinsare aligned with the respective bayonet slots or grooves. Thus thedirection of operation for the operating key may be selected as desiredand the extraction key will automatically operate the corresponding lockin the opposite direction irrespective of which direction is selectedfor the operating key.

The present invention also provides that the extraction key may directlyremove a lock cylinder from the front of the housing without requiringremoval of the housing and permits lock cylinders to be easily changedfor altering the control sequence of apparatus at different locations.In addition the present invention enables multiple locks to be easilyprovided with each under control of a different operating key forinsuring a desired sequence of lock operations.

It is, therefore, among the primary objects of the present invention toprovide an improved or more economical lock extraction apparatus orassembly.

It is another object of the present invention to provide an improvedand/or more economical key interlock system or method for controllingthe operation and the release of any one of a plurality of lockcylinders.

Other objects and the features of the present invention will becomeapparent on examination of the following specification and claimstogether with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a lock assembly incorporating theprinciples of the present invention.

FIG. 2 is a front elevational view of the assembly shown in FIG. 1.

FIG. 3 is an end elevational view of the assembly shown in FIG. 1.

FIG. 4 is a sectional view taken generally along the line 4--4 in FIG.2.

FIG. 5 is a sectional view taken generally along the line 5--5 in FIG.2.

FIG. 6 is an enlarged fragmentary view of a portion of the lock assemblyshown in FIG. 1.

FIG. 7 is a front elevational view of an operating key.

FIG. 8 is a sectional view taken through the line 8--8 in FIG. 5.

FIG. 9 is a rear elevational view of a lock cylinder.

FIG. 10 is a front end elevational view of a master key.

FIG. 11 is a sectional view of a portion of a master key.

FIG. 12 is a sectional view taken longitudinally of the housing andbolt; and

FIG. 13 is an exploded isometric view of the lock assembly shown in FIG.1 with the housing partially broken away together with the respectiveoperating keys and the master key.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIGS. 1-3 a lock assembly incorporating the principles of the presentinvention is indicated by the reference character 10. The lock assembly10 includes a housing 12 having spaced parallel hollow bosses 14 and 16each defining a passage 17 in which a respective combination lockcylinder 18 and 20 of the axially movable tumbler type is secured forcontrolling a bolt 22.

Each lock cylinder or cylinder assembly 18 and 20 is operated by arespective operating key such as 24 having tumbler control means oroperating pins 26 as seen in FIGS. 7 and 13, and are removed from therespective housing boss 14 and 16 by a common lock cylinder extractionkey 28 having tumbler control means or operating pins 30 as seen inFIGS. 10, 11 and 13.

The combination lock cylinders 18 and 20 are of an axial tumbler typesuch as manufactured by Van Lock Co., 3609 Church St., Newton,Cincinnati, Ohio 54244 and shown in respective brochures such as thosepublished by the Van Lock Company entitled "HOW TO CHANGE COMBINATIONSON VAN LOCK & KEY," "BEVERAGE TRUCK DOOR LOCK SYSTEMS," or "VENDINGMACHINE & BEVERAGE TRUCK DOOR LOCK SYSTEMS."

The locks or lock cylinders 18 and 20 as best seen in FIG. 5 eachinclude an outer sleeve or annular member 32 carrying a pair ofcoaxially adjacently spaced tumbler barrels 34 and 36 received in anaxial passage 38 of a sleeve member 32. A plurality of spirally spacedtumbler pins 40 extend axially in respective passages 42 of the endbarrel 36 from one end face 44 of the end barrel 34. End face 44 issubstantially coincident with a corresponding end of sleeve 32 and theopen end of the respective boss 14 or 16.

The pins 40 each have a stop shoulder thereon engaged with a stopshoulder in the respective passage 42 under the bias of respectivesprings 46 transmitted through respective aligned pin 48 and arespective intermediate or master pin 50 so that the ends of pins 40 aresubstantially flush with the end face 44 of the end tumbler barrel 34.The springs 46 and a portion of pins 48 are located in a respectivepassage 52 of the inner barrel 36 with the pins 48 extending acrossadjacent or mating end faces of barrels 34 and 36 into respectivepassages 42 to prevent relative rotation therebetween in the normal orlocked condition.

The inner barrel 36 is annular and a rearwardly extending shaft 54 onbarrel 34 extends through barrel 36. The shaft 54 has an annular surfacerecess substantially coincident with a radially inwardly extendingshoulder of the sleeve passage 38 for receiving a retaining member 58.Member 58 seats against the shoulder in passage 38 and secures a closuremember 60 to the adjacent end of barrel 36 for closing the correspondingend of each passage 52 and holding the springs 46. The barrel 36 issecured to sleeve 32 by means of a radially extending threaded member 62and with the retaining member capturing shaft 54 between the barrel 36and the shoulder in passage 38, the barrel 34 cannot be moved axiallyfrom sleeve 32 to permit changing the tumbler pins without firstremoving member 62.

The shaft 54 extends into a reduced diameter portion of passage 38 insleeve 32 and has a non-circular end for receipt in a non-circular endof a sleeve shaft 64 projecting forwardly from a cylindrical drive plate66 so that the drive plate 66 rotates with shaft 54, when tumbler barrel34 is rotated by the respective operating key 24 or a master key 28.

The drive plate 66 seats against the end of the sleeve 32 and isretained against axial movement from the sleeve by pins such as 68extending radially through sleeve 32 and having a projecting end engagedin a peripheral recess 70 of the shaft 64. A C ring 72 fitted in aperipheral recess of the sleeve shaft 64 retains the pins 68 in thesleeve 32, while permitting rotation of the shaft 64 and the drive plate66. Plate 66 in turn seats against the inner end of a key 74 formed onthe inner periphery of each boss 14 and 16 to retain the respective lockcylinder in the boss.

Sleeve 32 has a slot 76 in the outer periphery of the sleeve forreceiving a key 74 of the respective boss 14 or 16 so that the sleeve 32cannot rotate relative the boss. With pins 48 extending across themating or engaged faces of barrels 34 and 36, the barrel 34 likewisecannot rotate relative barrel 36, sleeve 32 or the respective boss. Theshaft 54 is therefore also held immobile, to in turn hold the shaft 64and the drive plate 66 stationary.

It will be noted that the drive plate 66 is located behind the key 74 sothat the periphery of the plate is in inteferring relationship with thekey or boss 74 to prevent withdrawal of the lock cylinder assembly 18 or20 from the respective boss. A slot 78 is provided in the periphery ofeach drive plate 66 for alignment with the boss 74, when the drive plateis rotated in the proper direction by a lock cylinder extraction key 28,as will be explained, to permit withdrawal of the lock cylinder 18 or 20from the boss.

The sleeve 32 is provided with a reduced diameter annular portion 80axially coincident with barrel 34 and terminating with face 44 at theend face of the respective boss 16 or 18. The reduced diameter portion80 defines an annular space or passage 82 for receipt of a respectiveannular rim wall 84 or 86 on the end of either a cup shaped operatingkey 24 or a cup shaped lock removal master key 28 respectively.

The outer periphery of the reduced diameter portion 80 is also providedwith a pair of diametrically opposed axially extending bayonet typearcuate grooves or slots 88 each communicating with one groove of a pairof bayonet type receiving grooves 90 and 92 formed in the periphery ofportion 89. Grooves 92 are offset axially from grooves 90 toward ashoulder on sleeve 32 and extend in the opposite angular direction fromgrooves 90 and both pair of grooves 90 and 92 extend through arespective pre-determined angular distance. The arcuate or angularextent of the groove 90 is selected in accordance with the desired anglethrough which it is desired to rotate or move a pin 96 or 98 projectingfrom one end raidl face of the respective drive plate to control thetravel of bolt 22 accordingly. The angle through which the slots 92extend is determined by the distance through which plate 66 is to berotated for aligning slot 78 with key 74. Preferably grooves 92 extendfor 45° so that rotation of the drive plate through 45° counterclockwisefor example aligns slot 78 with key 74 to enable withdrawal of the lockcylinder. Grooves 90 may then extend through an angle of 150° or more inthe clockwise direction to permit a large angular movement of the driveplate without aligning slot 78 with key 74. Other angles and directionsof rotation may of course be chosen.

Grooves 90 of each lock cylinder are adapted to receive a pair ofdiametrically opposed bayonent pins 100 at the end of the annular wall84 of a respective operating key 24 and the grooves 92 of each lockcylinder are adapted to receive a pair of bayonet pins 102 at the end ofannular wall 86 of the master key 28.

The cup shaped keys 24 and 28 each have a back wall 104 and 106respectively from which circumferentially spaced axially projectingtumbler operating pins 26 and 30 project in one direction and anoperating handle 108 projects in the other direction. The pins 26 extendaxially to different lengths as compared to other pins 26 of the samekey in accordance with the combination of the respective lock. The pins30 of the extraction key extend axially in accordance with a standardand predetermined or master pattern universal or common to a pluralityof operating keys and locks. The length of the annular wall 84 or 86from the back wall 104 or 106 is chosen so that the bayonet pins 100 ofeach operating key 24 align only with grooves 90, when the back wall 104of the key is fully engaged with the end face 44 and the sleeve endface. Wall 104 therefore acts as a stop wall while the orientation ofthe tumbler operating pins polarizes the bayonet pins 100 relativealignment with grooves 90.

Likewise, the length of annular wall 86 on key 28 is chosen so thatbayonet pins 102 align with grooves 92 only when properly polarized andwhen the stop wall 106 is fully engaged with face 44. Therefore anoperating key 24 cannot be used to rotate the drive plate for removingthe lock cylinder and an extraction key 28 cannot be used to operate thedrive plate for controlling the bolt.

The housing 12 has an end flange 110 at one end and a pair of spacedhollow mounting bosses 112 adjacent the end of housing 12 oppositeflange 110 for enabling the housing 12 to be mounted on a support. Thehousing 12 also includes a semi-cylindrical passage 114 as best seen inFIGS. 4 and 12 for receiving the bolt 22, which extends transverse tothe hollow bosses 14 and 16 for communication with the blind end of eachpassage 17 in the bosses. The number of bosses 14 and 16 and lockcylinders are selected as desired or needed in accordance with thenumber of locks, which are required to be operated for controlling thebolt travel. Thus, it may be required that three, four or even morelocks be operated before the bolt can be used to enable selectedapparatus in which case each lock will be operated by a respective key,which is retained in the lock before bolt travel is permitted.

The bolt 22 is provided with a semi-cylindrical portion extending inpassage 114 past the end of passage 17 to prevent relative rotation andboth the bolt and passage 114 have a full cylindrical end portionadjacent the end opposite flange 110. The flat faces defined by thesemi-cylindrical bolt and passage portions prevent rotation of the boltand since the communicating end of passage 17 is larger than the bolt, aspace 116 is provided above the bolt by each passage 17. The end of thebolt 22 adjacent flange 110 is adapted to engage a plunger 118, forexample, of a switch carried by flange 110, or it may engage a bolt ofanother housing engaged with flange 110 in response to movement of thebolt to a corresponding end or limit position. The other cylindrical endof the bolt on movement from the other end of the housing may operate orpermit the operation or disablement of selected apparatus or machinery.

The flat face of the semi-cylindrical portion of the bolt faces thepassages 17 and is provided with a pair of spaced radially extendingrecesses 120 and 122 aligned with a respective passage 17 for receivinga respective actuator pin 96 and 98 projecting from the rear surface ofa respective rotatable drive plate 66. The radial edges of recess 120are spaced apart a greater distance than the radial edges of recess 122and recess 120 has a stop edge 124 and an inclined lower radial edgesurface 126 to accommodate the movement of the pin 96 for enablingrelease of the lock cylinder or assembly from the respective boss.

Recess 122 is just large enough to accommodate pin 98, and its radialedges are spaced for engaging pin 98 along a line generally tangent tothe rotational arc of pin 98 to permit pin 98 to move the bolt from thehousing or to retract the bolt into the housing only when pin 98 isdisengaged from stop surface 124.

In addition a recess 128 is provided in the arcuate periphery bolt 22for engagement with one leg of a spring 130. Spring 130 is located in arecess of the housing adjacent the end of boss 16 to restrain the boltagainst disengagement from the housing in the event the housing passageis aligned vertically and both lock cylinders 18 and 20 are removed.

Normally the bolt 22 in the arrangement shown herein cannot be retractedinto the housing 12 when the operating key for each lock cylinder iswithdrawn. Pin 96 is then located to engage radial edge 124 of the bolt.Therefore, if an attempt should be made to operate lock cylinder 20 witha respective operating key rotation of pin 98 to move the lock isprevented.

Thus to operate the bolt 22, the wall 84 of an operating key 24corresponding to cylinder 18 is engaged over reduced portion 80 ofcylinder 18 with pins 100 aligned with grooves 88. The wall 84 is movedover barrel 34 until face 44 engages wall 106. At that time pins 100 arealigned with grooves 90 and if the pins 100 are properly inserted, theaxially offset spirally spaced pins 26 move respective pins 40, 48 and50 axially against the bias of spring 46 to align the interface of pins48 and 50 with the interface of barrels 34 and 36. This permits relativerotation between the barrels 34 and 36. The key 24 is therefore rotatedwith pins 100 moving freely in slots 90 and the pins 30 rotate barrel 34and shaft 54 clockwise, for example, as seen in the drawings, until thekey pins engage the groove ends.

As shaft 54 rotates, it in turn rotates shaft 64 to rotate the driveplate 66 and pin 96 to a position indicated at 132 in space 116 abovethe bolt. At that time pins 100 are engaged with the stop ends orsurfaces at the ends of respective grooves 90 and key 24 must beretained in position before another key such as 24 corresponding tocylinder 20 can be used to retract the bolt. Thus operating personnelare assured that cylinder 16 is properly operated before cylinder 20 canbe operated, as key 24 associated with cylinder 16 cannot be withdrawnwithout moving pin 96 back to its original position and engaged withsurface 124.

Another key indicated at 136 in FIG. 13 is then used to operate cylinder20 in a manner similar to that described for key 24 and cylinder 18 toin turn rotate pin 98 against an adjacent radial edge of recess 122 andmove the bolt 22 fully into the housing. Key 136 now cannot be retractedfrom the cylinder without rotating the same from the end stop surfacesof the corresponding grooves 90 and this would return the bolt 22 to itsfully extended position. The key 24 is also retained in position, as therecess 120 is now fully withdrawn from alignment with boss 14 and islocated adjacent the flange 119 where the bolt may operate appropriateapparatus such as plunger 118. A clear indication of the condition ofthe associated apparatus is thus thus provided.

To retract the operating keys 24 and 136, the key 136 is rotated fromthe end surfaces of the respective grooves 90 to align pins 100 withslots 88 to permit withdrawal of key 136. The recess 120 of bolt 22 isnow aligned with boss 14 and key 24 is operated to move pin 96 intorecess 120 and align its pins 100 with the respective slots 88 forenabling withdrawal of the key and thus clearly indicate the conditionof the locks. This ensures that bolt 22 is fully extended or in apredetermined condition before other apparatus located in anotherportion of the plant can be enabled, since the other apparatus mayrequire key 24 or 136 to be used to enable the same. This ensures thateach piece of apparatus is controlled in the proper sequence and permitschanges in the sequence by using lock cylinders requiring the same keyat different locations without necessitating a physical interconnectionbetween the apparatus.

To remove either of the lock cylinders 18 or 20 for replacement or forchanging of the tumbler pin arrangement, the extraction key 28 isutilized. Changing of the lock cylinder may be required, for example,when it is desired to utilize the cylinder 18 or 20 and its respectivekey to control another piece of apparatus or if it is desired to placebolt 22 under control of still another key.

The annular wall 86 on the extraction key 28 is moved into overlappingrelationship with sleeve portion 80 of either cylinder 18 or 20. Thepins 102 move in slots 88 until the front face 44 of barrel 34 engagesstop wall 106, assuming each pin 102 is in a respective one of slots 88.The pins 102 are then aligned with grooves 92 and pins 30 have moved thetumbler pins 40, 48 and 50 to a position in which the interface betweenpins 40 and 50 is located at a position axially coincident with theengaged radial faces of barrels 34 and 36. The axial extent of the pins30 is, of course, chosen to operate pins 40 of each cylinder 18 and 20to the desired axial position. Since seven pins are chosen to providethe operating combination for each key, the key 28 can operate anextremely large number of locks with different tumbler pin combinations,although as a practical matter most situations require an extraction keyoperating only up to 50 different combination locks.

When key 28 is rotated, the pins 30 rotate barrel 34 to rotate the driveplate 66 in the direction opposite to that of the operating key. Thisrotation can only occur in a direction opposite the direction of initialrotation of the respective operating key to ensure that the associatedapparatus cannot be properly conditioned. When the pins 102 engage theend or stop surfaces of the respective grooves 92, the slot 78 in thedrive plate is automatically aligned with boss 74 and slot 76. Rotationof the drive plate of cylinder 20 also disengages the pin 98 from thebolt by movement into the space 116 above the bolt, while rotation ofcylinder 16 moves the pin 96 into the enlarged space defined by boltsurface 126. With key 28 engaged in the groove 92 the lock cylinder 18or 20 is now simply retracted from the respective boss passage 17 topermit replacement of the cylinder or change of the tumbler pins It willbe noted that the cylinders can be extracted only when the bolt is in aselected position such as shown in FIG. 12, as pins 96 and 98 cannot beotherwise moved into the space below surface 132 and the space 116respectively.

To reinsert a lock cylinder in a boss, the key 28 is associated with thelock cylinder to rotate the barrel 34 and drive plate 66 for aligningslot 78 with slot 76 and the lock cylinder inserted in the boss untilthe drive plate bottoms against the bolt at which time, slot 78 is pastthe key 74. The key 28 is now rotated to align pins 102 with grooves 88,which in turn rotates the drive plate 66 for engaging pin 96 or 98 withthe appropriate bolt recess while moving slot 78 from alignment with thekey 74. The key 28 may now be simply retracted from the lock cylinder,which is retained in the boss by the interference of key 72 with driveplate 66.

It will be noted that the described housing and bolt arrangement permitfacile additions or changes, since the housings are easily stacked andbolts of appropriate length and configuration facily manufactured andinserted.

The foregoing is a description of an improved and more economical lockextraction apparatus or assembly whose inventive concepts are notlimited to the described embodiment or environment, but are believed setforth in the accompanying claims.

What is claimed is:
 1. A combination comprisinga plurality ofcombination lock cylinders, a selected housing for each lock cylinder, acommon bolt for said lock cylinders having a selected position, arespective tumbler barrel carried by each lock cylinder and adapted toreceive a respective operating key, a plurality of axially movabletumbler pins carried by each lock cylinder to prevent rotation of arespective tumbler barrel and movement of said bolt from said selectedposition, said pins moved along the axis of a respective cylinder by arespective received operating key to enable initial rotation of arespective tumbler barrel in a respective initial direction forcontrolling said bolt to enable movement of said bolt from said selectedposition, each lock cylinder also adapted to receive a lock cylinderextraction key common to each cylinder for axially moving said pins toenable initial rotation by said extraction key of the respective barrelin a direction opposite each respective direction, means effective onlyin response to said bolt being in said selected position for enablinginitial rotation of the respective barrel by said extraction key only ina direction opposite the respective direction and for enablingextraction of the respective lock cylinder from the selected housing. 2.The improvement claimed in claim 1 in which said means enabling initialrotation by said extraction key includes a first bayonet groove for eachcylinder extending in a direction opposite the respective direction forengagement only by said lock cylinder extraction key.
 3. For use with aplurality of combination lock cylinders each secured in a selectedhousing and adapted to receive a respective operating key for axiallymoving a plurality of axially movable tumbler pins carried by each lockcylinder to enable initial rotation of a tumbler barrel in a respectivedirection for controlling a bolt with each lock cylinder also adapted toreceive a lock cylinder extraction key common to each cylinder foraxially moving said pins to enable rotation of the respective barrel,the improvement comprising;means on each lock cylinder enabling initialrotation of the respective barrel by said extraction key in a directionopposite the respective direction for enabling release of the respectivelock cylinder from the selected housing, said means including a firstbayonet groove for each cylinder extending in a direction opposite therespective direction for engagement only by said lock cylinderextraction key, each cylinder having a second bayonet groove extendingin the respective direction, each said second bayonet groove offsetaxially relative said lock cylinder from the respective first groove forengagement only by a respective operating key.
 4. In the improvementclaimed in claim 3 a drive plate for each lock cylinder adapted to berotated in one direction by a respective barrel for controlling saidbolt, and means on said drive plate rotated to a selected position bysaid barrel in response to the rotation of said barrel in the oppositedirection for enabling release of said cylinder from said housing.
 5. Inthe improvement claimed in claim 4, an axially extending slotinterconnecting said first and second grooves.
 6. The improvementclaimed in claim 5 in which each groove has a stop end for limitingrotation to a corresponding angle.
 7. The improvement claimed in claim 6in which each key is rotated in a direction from a respective stop endfor rotating said drive plate in a corresponding direction and forenabling release of said key from the respective groove.
 8. In theimprovement claimed in claim 5 in which each key has a bayonet pin and aplurality of tumbler control pins.
 9. The improvement claimed in claim 8in which each lock cylinder includes an annular sleeve in which eachbayonet groove is formed and each key includes a back wall forsupporting said tumbler control pins with an annular wall adapted toreceive said sleeve and supporting the respective bayonet pin.
 10. Theimprovement claimed in claim 9 in which the annular wall on each keycarries the respective bayonet pin and the bayonet pin on each operatingkey is located one selected axial distance from the respective back walland the bayonet pin on said master key is located another axial distancefrom the respective back wall.
 11. The improvement claimed in claim 10in which said back wall positions each bayonet pin in alignment with arespective bayonet groove and one of said pins is adapted to move insaid axially extending slot past one of said bayonet grooves.
 12. Theimprovement claimed in claim 4 in which one housing carries a pair oflock cylinders and a bolt having a semi-cylindrical portion with a pairof spaced radially extending recesses formed in the flat face of saidsemi-cylindrical portion, and the drive plate for each cylinder has arespective operating pin projecting into a respective one of saidrecesses for controlling the movement of said bolt.
 13. The improvementclaimed in claim 12 in which the edges of one of said recesses arespaced for enabling rotation of the respective drive plate to engage arespective edge for moving said bolt in each direction and an edge ofthe other recess is spaced for engaging the operating pin of the otherdrive plate in response to rotation of the other drive plate is forpreventing movement of said bolt in a respective direction.
 14. Aninterlock system for use with a plurality of combination lock cylinderseach carried in a respective housing portion and each having a tumblerbarrel carrying a plurality of axially movable tumbler pins adapted toenable rotation of the respective tumbler barrel in a respectivedirection for controlling a bolt and rotation of said barrel in theopposite direction for releasing the respective lock cylinder from saidhousing, the improvement comprising:an operating key for each cylinderwith each operating key having tumbler control means for moving thetumbler pins of the respective cylinder to a selected position forenabling rotation of the respective barrel, first means for thereafterenabling initial rotation of said operating key to rotate the respectivebarrel only in a respective direction to control said bolt, anextraction key having tumbler control means for moving the tumbler pinsof each of said lock cylinders to another selected position for enablingrotation of the respective barrel of each cylinder, and second means forthereafter enabling initial rotation of said extraction key to initiallyrotate the respective barrel only in a direction opposite saidrespective direction for enabling the release of the respective lockcylinder from the respective housing.
 15. An interlock system for usewith a plurality of combination lock cylinders each carried in arespective housing portion and each having a tumbler barrel carrying aplurality of axially movable tumbler pins adapted to enable rotation ofthe respective tumbler barrel in a respective direction for controllinga bolt and rotation of said barrel in the opposite direction forreleasing the respective lock cylinder from said housing, theimprovement comprising;an operating key for each cylinder with eachoperating key having tumbler control means for moving the tumbler pinsof the respective cylinder to a selected position for enabling rotationof the respective barrel, first means for thereafter enabling initialrotation of said operating key to rotate the respective barrel only in arespective direction to control said bolt, an extraction key havingtumbler control means for moving the tumbler pins of each of said lockcylinders to another selected position for enabling rotation of therespective barrel of each cylinder, second means for thereafter enablinginitial rotation of said extraction key to rotate the respective barrelonly in a direction opposite said respective direction for enabling therelease of the respective lock cylinder from the respective housing,said first means comprising a first pair of bayonet grooves extending ina selected angular direction and a first pair of bayonet pins on eachoperating key with each bayonet pin adapted to be engaged in arespective one of said pair of grooves to enable rotation of theoperating key, and said second means comprises a second pair of bayonetgrooves offset axially relative said first pair of bayonet grooves andextending in an opposite angular direction to said selected angulardirection, and a pair of bayonet pins on said extraction key forengagement in a respective one of said second pair of bayonet grooves.16. The interlock system claimed in claim 15 in which each lock cylinderincludes an end face and an annular recess in which said bayonet groovesare located with one groove of each pair interconnected by a commongroove extending axially to said end face for alternately receiving arespective bayonet pin on an operating key and on said extraction key.17. The interlock system claimed in claim 16 in which each key has a cupshape with a back wall adapted to engage said end face and each saidtumbler control means comprises a plurality of pins projecting from saidback wall for moving said tumbler pins axially of said sleeve and theannular wall of said cup shape carries said pins for engaging arespective pair of grooves in response to said back wall engaging saidend face.
 18. The interlock claimed in claim 17 in which each lockcylinder has a drive plate rotated in response to the rotation of therespective tumbler barrel, means on each drive plate for controllingsaid bolt in one manner in response to initial rotation in a selecteddirection of the respective barrel and in another manner in response tosubsequent lock cylinder and a bayonet key axially positioned onrotation in a reverse direction.
 19. The interlock system claimed inclaim 18 in which said drive plate includes means for releasing saidlock cylinder from said housing in response to initial rotation of saidbarrel in said reverse direction.
 20. The interlock system claimed inclaim 19 in which one pair of bayonet grooves extend angularly adifferent distance than the other pair of bayonet slots and each groovehas an end face for terminating rotation.
 21. The system claimed inclaim 14 in which each lock cylinder is released from the respectivehousing portion in response to said initial rotation by said extractionkey to a respective predetermined position and axial movement in onedirection by said extraction key to axially move the respective cylinderfrom said housing portion by said extraction key.
 22. In the systemclaimed in claim 14, means for enabling rotation of one tumbler barreland movement of said bolt by one operating key only in response torotation of another tumbler barrel to a predetermined position byanother operating key,and means for preventing disengagement of saidother operating key from the respective lock cylinder in response tomovement of said bolt in one direction.
 23. In the system claimed inclaim 22, means for preventing disengagement of said one operating keyfrom the respective lock cylinder in response to the rotation of therespective barrel for moving said bolt in said one direction.
 24. Amethod for changing combination locks of the axially movable pin typeused in controlling switchgear comprising the steps of providing:ahousing carrying a plurality of locks each having a rotatable tumblerfor controlling a bolt movable to alter the condition of saidswitchgear, an operating key for each lock adapted to initially rotatethe respective tumbler in a respective direction, an extraction keycommon to each lock adapted to rotate each tumbler for enablingdisengagement of each lock from said housing, and means for enablingsaid extraction key to initially rotate each tumbler only in a directionopposite said respective direction to prevent an alteration in thecondition of said switchgear in response to rotation of said tumblerbarrel by said extraction key.